JP2016039265A - Photodetector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase a current amplification factor of a photodetector.SOLUTION: A photodetector 1 includes: an electrode 5; an insulating film 7; and a semiconductor layer 3b including a first semiconductor region 9, a second semiconductor region 11 and a third semiconductor region 13. The electrode 5 is embedded in the semiconductor layer 3b in a first direction from the surface toward the inner part of the semiconductor layer 3b. The insulating film 7 is arranged between the electrode 5 and the semiconductor layer 3b. The N-type first semiconductor region 9 is arranged on the surface of the semiconductor layer 3b. The P-type second semiconductor region 11 is adjacent to the insulating film 7 and the first semiconductor region 9. The N-type third semiconductor region 13 is adjacent to the second semiconductor region 11. As for the P-type impurity concentration of the second semiconductor region 11, the P-type impurity concentration in a second region in a region 11 closer to the insulating film 7 than the first region is lower than the P-type impurity concentration in a first region in a region 11 separated from the insulating film 7 in a second direction perpendicular to the first direction.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a light detection element.

  As a photodetecting element, a photodiode is easy to manufacture and can detect a stable photocurrent. Therefore, photodiodes are often used as light detection elements. However, the photodiode has a weak photocurrent obtained during light irradiation. Therefore, a photodiode having a large light receiving area is required to improve the light receiving sensitivity at low illuminance.

  A phototransistor having a bipolar structure has a characteristic that when a photocurrent obtained by a photodiode formed between a collector and a base is output from an emitter, the current can be amplified by physical properties of the bipolar structure. A phototransistor having a vertical bipolar structure in which the photocurrent with respect to the light intensity is made variable by making the current amplification factor variable by making use of this feature is known (for example, see Patent Document 1).

  The conventional photodetection element has a problem that, for example, the current amplification factor for increasing the photocurrent is not sufficient.

  An object of the present invention is to increase the current amplification factor of a photodetecting element.

  The photodetecting element according to the present invention includes an electrode, an insulating film, and a semiconductor layer including a first semiconductor region, a second semiconductor region, and a third semiconductor region, and the electrode extends from the surface of the semiconductor layer to the inside. And embedded in the semiconductor layer along a first direction, the insulating film is disposed between the electrode and the semiconductor layer, and the first semiconductor region has a first conductivity type. And the second semiconductor region is of a second conductivity type, is disposed adjacent to the insulating film and the first semiconductor region, and the third semiconductor is disposed on the surface of the semiconductor layer. The region is of a first conductivity type and is disposed adjacent to the second semiconductor region, and an impurity concentration of the second conductivity type impurity of the second semiconductor region is a second orthogonal to the first direction. The second semiconductor is away from the insulating film in the direction of For the first region of the region and the second region of the second semiconductor region closer to the insulating film than the first region, the impurity concentration of the second region is higher than that of the first region. It is characterized by being lower than the impurity concentration.

  The photodetecting element of the present invention can increase the current amplification factor of the photodetecting element.

It is a schematic sectional view for explaining an example. It is a schematic plan view for demonstrating the Example. It is a graph which shows the impurity concentration profile of the horizontal direction of the semiconductor substrate surface vicinity in the photon detection element of the Example. It is a graph which shows the impurity concentration profile of the depth direction in the photon detection element of the Example. It is a schematic sectional drawing for demonstrating an example of the manufacturing process for producing the Example. FIG. 4 is a schematic cross-sectional view for explaining a step subsequent to FIG. 3. FIG. 5 is a schematic cross-sectional view for explaining a step subsequent to FIG. 4. It is a schematic sectional drawing for demonstrating an example of the conventional photon detection element. It is a schematic sectional drawing for demonstrating the other example of the conventional photon detection element. 10 is a graph showing a horizontal impurity concentration profile in the vicinity of the surface of the semiconductor substrate in the light detection element shown in FIG. 9. It is a schematic sectional drawing for demonstrating another Example. It is a schematic sectional drawing for demonstrating an example of the manufacturing process for producing the Example. FIG. 13 is a schematic cross-sectional view for explaining a process following the process in FIG. 12. Furthermore, it is a schematic sectional drawing for demonstrating another Example. It is a graph which shows the impurity concentration profile of the horizontal direction of the base area | region in the photodetector of the Example.

  In the photodetecting element of the present invention, the first conductivity type means P type or N type, and the second conductivity type means N type or P type opposite to the first conductivity type.

  In the photodetecting element of the present invention, for example, the first semiconductor region (for example, the emitter region) may be disposed apart from the insulating film (gate insulating film). According to this aspect, in the photodetector according to the present invention, the first semiconductor region, the second semiconductor region (for example, the base region), the third semiconductor region (for example, the collector region), the electrode (for example, the gate electrode), and the insulating film are formed. There is no parasitic MOS transistor structure. In this aspect, the main component of the dark current in the light detection element of the present invention is a leak current generated in the light detection element. Therefore, the aspect in which the first semiconductor region is arranged away from the insulating film in the photodetecting element of the present invention can suppress dark current as compared with the case where the parasitic MOS transistor structure is present. In the photodetecting element of the present invention, the first semiconductor region may be disposed in contact with the insulating film.

  In the photodetector according to the aspect of the invention in which the first semiconductor region is arranged apart from the insulating film, for example, in the second semiconductor region, the second region is adjacent to the insulating film, One region may be adjacent to the first semiconductor region, and the impurity concentration of the second conductivity type impurity may be lowered from the first region toward the second region.

  Further, for example, the position of the bottom of the first semiconductor region in the first direction may be deeper than a position that is half the depth of the second semiconductor region in the first direction. However, in the present invention, the position of the bottom of the first semiconductor region in the first direction may be shallower than a position that is half the depth of the second semiconductor region in the first direction.

  In the configuration in which the first semiconductor region is disposed apart from the insulating film, for example, the first semiconductor region is formed of a semiconductor material embedded in the semiconductor layer from the surface to the inside of the semiconductor layer. Is realized. However, in the present invention, the first semiconductor region is not limited to one formed of an embedded semiconductor material. In the present invention, the first semiconductor region may be a partial region of the semiconductor layer and a region doped with a first conductivity type impurity.

  When the first semiconductor region is disposed away from the insulating film, the area of the boundary between the emitter region (first semiconductor region) and the base region (second semiconductor region) of the bipolar transistor structure increases. In addition, the area where the boundary between the emitter region and the base region and the electrode embedded via the insulating film face each other increases. Similarly, the area where the electrode is opposed to the depletion layer extending in the second semiconductor region by applying a voltage to the electrode increases. Therefore, the current path during bipolar operation is expanded and the current amplification factor is increased. This effect is particularly prominent in the configuration in which the bottom of the first semiconductor region is disposed at a deep position, for example, at a half position of the depth of the bottom of the second semiconductor region.

  In the photodetector of the present invention, for example, the impurity concentration of the second conductivity type impurity in the second semiconductor region decreases from the first semiconductor region side to the third semiconductor region side in the first direction. You may be allowed to. However, the distribution of the impurity concentration of the second conductivity type impurity in the second semiconductor region in the first direction is not limited to this. The distribution of the impurity concentration may be uniform, for example, or other concentration distribution.

Next, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic cross-sectional view for explaining an embodiment. FIG. 2 is a schematic plan view for explaining the embodiment. The cross section in FIG. 1 corresponds to the position AA in FIG.

  A plurality of light detection elements 1 are formed on the semiconductor substrate 3. The semiconductor substrate 3 is composed of, for example, an N-type silicon substrate 3a (N + substrate) into which an N-type impurity is introduced, and an N-type epitaxial layer 3b (semiconductor layer) formed on the surface by epitaxial growth. In the present invention, the semiconductor layer is not limited to an epitaxial layer. In the present invention, the semiconductor layer may be, for example, a bulk silicon layer, a semiconductor layer made of another semiconductor material, or may be formed of a plurality of stacked semiconductor layers.

  The plurality of light detection elements 1 are arranged in a matrix, for example. The photodetecting element 1 includes a gate electrode 5 (electrode), a gate insulating film 7 (insulating film), an emitter region 9 (first semiconductor region), a base region 11 (second semiconductor region), and a collector region 13 (third semiconductor region). ).

  The gate electrode 5 is embedded in the epitaxial layer 3b along the depth direction (first direction) from the surface of the epitaxial layer 3b to the inside. For example, the gate electrode 5 has a width dimension of about 1 μm (micrometer) and a depth direction dimension of about 5 μm. For example, the gate electrode 5 is formed of polysilicon into which impurities are introduced. However, the material of the gate electrode 5 is not limited to polysilicon, and may be other semiconductor materials or conductive materials.

  The gate electrode 5 is arranged in a mesh shape in plan view, for example. The light detecting element 1 is formed for each region surrounded by the gate electrode 5.

  The gate insulating film 7 is disposed between the gate electrode 5 and the epitaxial layer 3b. The gate insulating film 7 insulates the gate electrode 5 from the epitaxial layer 3b. The gate insulating film 7 is formed of a silicon oxide film having a thickness of about 20 nm (nanometers), for example. However, the material of the gate insulating film 7 is not limited to the silicon oxide film, and may be any material that can insulate the gate electrode 5 and the epitaxial layer 3b.

  Emitter region 9 (N +) is formed on the surface of epitaxial layer 3b. It is provided for each photodetecting element 1. The emitter region 9 is formed by introducing an N-type impurity (first conductivity type) into the epitaxial layer 3b. The emitter region 9 is disposed away from the gate insulating film. The position of the bottom of the emitter region 9 is disposed at a position shallower than the bottom of the gate electrode 5.

  The base region 11 (P) is formed in the epitaxial layer 3 b between the emitter region 9 and the gate insulating film 7 and the epitaxial layer 3 b below the emitter region 9. The base region 11 is provided for each photodetecting element 1. The base region 11 is formed by introducing a P-type impurity (second conductivity type) into the epitaxial layer 3b. The base region 11 is adjacent to the gate insulating film 7 and the emitter region 9. The position of the bottom of the base region 11 is arranged at a position shallower than the bottom of the gate electrode 5.

  The collector region 13 (N−) is constituted by the epitaxial layer 3 b below the base region 11. The collector region 13 is adjacent to the gate insulating film 7 and the base region 11. The position of the bottom of the collector region 13 is arranged at a position deeper than the bottom of the gate electrode 5. The collector region 13 is continuous below the gate electrode 5 between the adjacent photodetectors 1. A position deeper than the bottom of the collector region 13 is formed by the epitaxial layer 3b.

  Interlayer insulating film 15 is formed on epitaxial layer 3b. A contact hole 17 is provided in the interlayer insulating film 15. The contact hole 17 is disposed at a position corresponding to the emitter region 9. The contact hole 17 is filled with a conductive material such as tungsten or aluminum.

  A metal wiring pattern 19 made of, for example, aluminum is formed on the interlayer insulating film 15. The metal wiring pattern 19 is electrically connected to the emitter region 9 through a conductive material filled in the contact hole 17. The potential of the gate electrode 5 is taken in a region not shown in FIGS. Although not shown, a final protective film or the like is formed on the interlayer insulating film 15.

  In the photodetecting element 1, a vertical bipolar transistor is formed by the emitter region 9, the base region 11, and the collector region 13. In the bipolar transistor, the current amplification factor changes when the width of the quasi-neutral base region changes. In the photodetecting element 1, by applying a voltage to the gate electrode 5, the width of the depletion layer near the gate electrode 5 in the quasi-neutral base region changes and the current amplification factor changes.

  In the photodetector 1, the gate electrode 5 is embedded in the epitaxial layer 3b along the first direction from the surface to the inside of the epitaxial layer 3b. Further, the impurity concentration of the P-type impurity in the base region 11 is higher than that of the first region of the base region 11 that is separated from the gate insulating film 7 in the second direction orthogonal to the first direction and the first region. In the second region of the base region 11 close to the gate insulating film 7, the impurity concentration of the second region is lower than the impurity concentration of the first region. Thereby, the photodetecting element 1 has a structure in which the base region 11 is easily depleted by applying a voltage to the gate electrode 5 as compared with the case where the distribution of the impurity concentration of the P-type impurity in the base region 11 is uniform. Therefore, the photodetecting element 1 can increase the current amplification factor by narrowing the base width over a wide range.

  FIG. 3 is a graph showing an impurity concentration profile in the horizontal direction in the vicinity of the surface of the semiconductor substrate in the photodetector according to the same example. FIG. 4 is a graph showing an impurity concentration profile in the depth direction in the photodetecting element of the example. In FIG. 3, the vertical axis represents the impurity concentration, and the horizontal axis represents the position from the center of the emitter region. In FIG. 4, the vertical axis represents the impurity concentration, and the horizontal axis represents the position from the surface of the semiconductor substrate.

  As shown in the impurity concentration profile of the base region 11, the base region 11 is inclined so that the impurity concentration of the P-type impurity decreases from the emitter region 9 side toward the gate electrode 5 side and the collector region 13 side. . The impurity concentration of the P-type impurity in the base region 11 is, for example, in the horizontal direction parallel to the surface of the semiconductor substrate 3 (second direction orthogonal to the first direction), on the center side (first region) of the base region 11. The impurity concentration on the end side (second region) of the base region 11 is lower than the impurity concentration of the base region 11. That is, in the vicinity of the gate electrode 5, the P-type impurity concentration of the base region 11 is low. By applying a voltage to the gate electrode 5, the base region 11 having a low impurity concentration in the vicinity of the gate electrode 5 is easily depleted, and the current amplification factor increases.

  Further, since the emitter region 9 is arranged away from the gate insulating film 7, the source of the parasitic MOS structure is offset. Therefore, no current flows as a MOS transistor. For example, when the photodetecting element 1 is operated as a phototransistor, the dark current is mainly a leakage current of a bipolar structure.

  Thus, the photodetecting element 1 of this embodiment can increase the current amplification factor by applying a voltage to the gate electrode 5, so that the current amplification factor can be increased without increasing the dark current, and the sensitivity during light irradiation can be increased. Can be high. The light detection element 1 can also detect a photocurrent at low illuminance.

  5 to 7 are schematic cross-sectional views for explaining an example of a manufacturing process for producing the embodiment of the photodetecting element described with reference to FIGS. 1 and 2. The numbers in parentheses in FIGS. 5 to 7 correspond to the numbers in parentheses of each process described below. An example of this manufacturing method will be described with reference to FIGS. 1 and 5 to 7.

(1) For example, a semiconductor substrate 3 having an N-type epitaxial layer 3b to be a collector region 13 on a low-resistance N-type silicon substrate 3a is prepared. The resistivity of the silicon substrate 3a is, for example, about 6 mΩcm (milliohm centimeter). The resistivity of the epitaxial layer 3b is, for example, about 1 Ωcm. The thickness of the epitaxial layer 3b is, for example, about 20 μm.

(2) A trench for embedding the gate electrode 5 is formed on the surface of the epitaxial layer 3b by a known method, doped polysilicon is buried in the trench portion via the gate insulating film 7, and an etch back process is performed. A gate electrode 5 is formed. For example, the trench has a width of about 1 μm and a depth of about 5 μm. The thickness of the gate insulating film 7 is, for example, about 20 nm. A mask film 21 is formed on the epitaxial layer 3b. The mask film 21 is, for example, a silicon oxide film having a thickness of 400 nm.

(3) An opening is formed in the mask film 21 at a position corresponding to the central portion of the formation region of the photodetecting element 1 (see FIG. 1) by photolithography and etching techniques.

(4) A P-type impurity (see + sign), for example, boron ions is implanted into the epitaxial layer 3b through the opening of the mask film 21 by an ion implantation technique. Boron implantation conditions are, for example, an acceleration energy of 30 keV and a dose of 3.5 × 10 ¹³ cm ⁻² .

(5) With the mask film 21 left, the base region 11 is formed by performing thermal diffusion treatment of the P-type impurity implanted in the step (4). The conditions for the thermal diffusion treatment are, for example, a temperature of 1150 ° C. and a time of 50 minutes. At this time, the P-type impurities constituting the base region 11 are diffused uniformly in the depth direction and the lateral direction, for example, about 1.5 μm around the opening portion of the mask film 21.

(6) An N-type impurity (refer to the symbol-), for example, phosphorus ions is implanted into the epitaxial layer 3b (base region 11) through the opening of the mask film 21 by an ion implantation technique. The phosphorus implantation conditions are, for example, an acceleration energy of 50 keV and a dose of 6.0 × 10 ¹⁵ cm ⁻² .

(7) With the mask film 21 left, the N-type impurity implanted in the step (6) is thermally diffused to form the emitter region 9. The conditions for the thermal diffusion treatment are, for example, a temperature of 900 ° C. and a time of 30 minutes. At this time, the N-type impurities constituting the emitter region 9 are diffused uniformly in the depth direction and the lateral direction, for example, by about 0.3 μm inside the base region 11 around the opening of the mask film 21.

(8) The mask film 21 is removed. Thereby, a self-aligned double diffusion structure in which the diffusion of the emitter region 9 and the base region 11 is diffused from the same position is completed.

(9) An interlayer insulating film 15, a contact hole 17, a metal wiring pattern 19, a final protective film, and the like are formed on the epitaxial layer 3b by a known method (see FIG. 1).

  In this example of the manufacturing method, the ion introduction for the emitter region 9 and the ion introduction for the base region 11 are performed using the same mask film 21, so that the production cost is lower than when separate mask films are used. Reduction can be achieved. However, when the photodetector of the present invention is manufactured, the first semiconductor region (emitter region 9) and the second semiconductor region (base region 11) may be formed using different mask films.

  In addition, the manufacturing method for manufacturing the photodetection element of the present invention, for example, the photodetection element 1 shown in FIG. 1, is not limited to the manufacturing method example described with reference to FIGS. 1 and 5 to 7.

  FIG. 8 is a schematic cross-sectional view for explaining an example of a conventional photodetecting element. In FIG. 8, the same parts as those in FIG.

  The photodetector 101 shown in FIG. 8 differs from the photodetector 1 shown in FIG. 1 in the structure of the emitter region 103 and the base region 105 from the structure of the emitter region 9 and the base region 11. .

  The emitter region 103 is formed on the entire surface surrounded by the gate electrode 5 on the surface of the epitaxial layer 3b. The emitter region 103 is disposed adjacent to the gate insulating film 7. The emitter region 103 has a uniform impurity concentration profile in the horizontal direction.

  The base region 105 is formed on the surface side of the epitaxial layer 3b before the trench for embedding the gate electrode 5 is formed. The base region 105 has a uniform impurity concentration profile in the horizontal direction.

  The impurity concentration profile in the depth direction of the emitter region 103, the base region 105, and the collector region 13 of the photodetector element 101 is, for example, the impurity in the depth direction of the emitter region 9, the base region 11, and the collector region 13 of the photodetector element 1. This is the same as the density profile (see FIG. 4).

  In the vertical bipolar structure of the photodetecting element 101, the emitter region 103 is in contact with the gate electrode 5 through the gate insulating film 7, so that the current amplification factor changes greatly by applying a voltage to the gate electrode 5.

  However, as shown in FIG. 8, a parasitic MOS transistor 107 exists in the light detection element 101. In the photodetecting element 101, when a voltage is applied to the gate electrode 5, the MOS transistor operates simultaneously with the bipolar operation. For this reason, when the photodetecting element 101 is operated as a phototransistor, a current flowing by the parasitic MOS transistor is added in addition to the photocurrent generated during light irradiation. For this reason, the photodetection element 101 has a large dark current, and the sensitivity at low illuminance is lower than that of the photodetection element 1 shown in FIG.

  FIG. 9 is a schematic cross-sectional view for explaining another example of a conventional photodetecting element. 9, the same parts as those in FIG. 1 or FIG.

  The photodetecting element 109 shown in FIG. 9 is different from the photodetecting element 1 shown in FIG. 1 in the structure of the base region 105 and the structure of the base region 11. The structure of the base region 105 is the same as the structure of the base region 105 of the photodetecting element 101 shown in FIG. The light detecting element 109 is different from the light detecting element 101 shown in FIG. 8 in that the emitter region 9 is arranged away from the gate insulating film 7.

  FIG. 10 is a graph showing an impurity concentration profile in the horizontal direction near the surface of the semiconductor substrate in the photodetecting element shown in FIG. In FIG. 10, the vertical axis represents the impurity concentration, and the horizontal axis represents the position from the center of the emitter region.

  In the photodetecting element 109, the impurity concentration profile in the horizontal direction of the base region 105 is uniform. The impurity concentration profile in the depth direction of the emitter region 9, the base region 105, and the collector region 13 of the light detection element 109 is, for example, the impurity in the depth direction of the emitter region 9, the base region 11, and the collector region 13 of the light detection element 1. This is the same as the density profile (see FIG. 4).

  In the photodetecting element 109, since the emitter region 9 is arranged away from the gate insulating film 7, the parasitic MOS transistor 107 included in the photodetecting element 101 shown in FIG. 8 is not formed. However, due to the emitter region 9 being spaced apart from the gate insulating film 7, the light detection element 109 has a smaller current amplification factor than the light detection element 101 shown in FIG.

  Furthermore, in the photodetecting element 109, the region where the depletion layer in the base region 105 spreads by applying a voltage to the gate electrode 5 is limited to a portion where the impurity concentration is low, that is, near the collector region 13 inside the epitaxial layer 3b. That is, even when voltage application to the gate electrode 5 is performed, the contribution to the change in the current amplification factor is small.

  Compared with the conventional photodetecting element 101 shown in FIG. 8 and the conventional photodetecting element 109 shown in FIG. 9, the photodetecting element 1 of the embodiment shown in FIG. The dark current of the vertical bipolar structure can be suppressed and the current amplification factor can be increased.

  FIG. 11 is a schematic cross-sectional view for explaining another embodiment. In FIG. 11, the same parts as those in FIG.

  In this embodiment, the emitter region 25 of the light detection element 23 is arranged at a deeper position than the emitter region 9 of the light detection element 1 shown in FIG. The position of the bottom of the emitter region 25 is preferably a position deeper than, for example, a position that is half the depth of the base region 11.

  The emitter region 25 is made of, for example, a semiconductor material embedded in the epitaxial layer 3b from the surface to the inside of the epitaxial layer 3b. The embedded semiconductor layer is, for example, N-type polysilicon.

  Since the emitter region 25 is formed to a deep position, the region of the gate electrode 5 facing the emitter region 25 becomes large. As a result, the area where the depleted portion of the base region 11 and the emitter region 25 are in contact with each other increases, so that the photodetecting element 23 further changes the current amplification factor as compared with the photodetecting element 1 shown in FIG. Can be bigger.

  In the photodetector 23 of this embodiment, the position of the bottom of the emitter region 25 is deepened by embedding a semiconductor material in the epitaxial layer 3b. However, the present invention is not limited to this. The emitter region 25 may be formed by an ion implantation technique. For example, in the step (6) described with reference to FIG. 6 (6), the emitter region 25 can be formed by changing the phosphorus implantation conditions. Further, the impurity implantation for forming the emitter region 25 may be performed in a plurality of times.

  12 and 13 are schematic cross-sectional views for explaining an example of a manufacturing process for producing the embodiment of the photodetecting element described with reference to FIG. The numbers in parentheses in FIGS. 12 and 13 correspond to the numbers in parentheses for each process described below. An example of this manufacturing method will be described with reference to FIGS. Since steps (1) to (5) of this manufacturing method example are the same as the above steps (1) to (5) of the manufacturing method example described with reference to FIGS. 1 and 5 to 7, Explanation is omitted.

(5) The gate insulating film 7, the gate electrode 5, the mask film 21, and the base region 11 are formed in the epitaxial layer 3 b constituting the collector region 13 by the same steps as the above steps (1) to (5).

(6) A recess 27 is formed on the surface of the epitaxial layer 3b by the etching technique using the mask film 21 as a mask. The recess 27 is formed to a depth that does not reach the bottom of the base region 11. The depth of the recess 27 is preferably deeper than half the depth of the base region 11.

  The etching conditions for forming the recesses 27 are preferably such that the etching selectivity between the epitaxial layer 3b and the mask film 21 is low, and the mask film 21 is etched simultaneously with the etching of the epitaxial layer 3b. . Note that the etching may be dry etching or wet etching.

  In this embodiment, the mask film 21 is also etched simultaneously with the etching of the epitaxial layer 3b, so that the thickness of the mask film 21 is reduced. By reducing the thickness of the mask film 21, the aspect ratio of the recess including the thickness of the mask film 21 in the recess 27 can be reduced. When the semiconductor material is embedded in the recess 27 in a later step, the semiconductor material This is because the embedded state of can be improved.

  However, it is preferable that the etching conditions are such that the mask film 21 remains when the formation of the recesses 27 is completed in consideration of the thickness of the mask film 21 before etching. This is because if the mask film 21 is completely removed during the etching process, the gate electrode 5 is exposed and a part of the gate electrode 5 may be etched away.

(7) A semiconductor material 25 a into which impurities are introduced is formed in the recess 27 and on the mask film 21. For example, the semiconductor material 25a is formed by depositing polysilicon into which phosphorus is introduced.

(8) The semiconductor material 25 a is etched back to remove the semiconductor material 25 a on the mask film 21, thereby forming the emitter region 25 made of the semiconductor material 25 a in the recess 27. The mask film 21 functions as an etching stop layer. As a result, the emitter region 25 and the base region 11 are self-aligned double diffusion. The mask film 21 is removed.

(9) An interlayer insulating film 15, a contact hole 17, a metal wiring pattern 19, a final protective film, and the like are formed on the epitaxial layer 3b by a known method (see FIG. 11).

  Note that the manufacturing method for manufacturing the light detection element of the present invention, for example, the light detection element 23 shown in FIG. 11, is not limited to the manufacturing method example described with reference to FIGS.

  FIG. 14 is a schematic cross-sectional view for explaining another embodiment. In FIG. 14, the same parts as those in FIG.

  In this embodiment, the emitter region 31 of the light detecting element 29 has a horizontal end parallel to the surface of the semiconductor substrate 3 as a gate compared to the emitter region 9 of the light detecting element 1 shown in FIG. It is in contact with the insulating film 7.

  FIG. 15 is a graph showing an impurity concentration profile in the horizontal direction of the base region in the photodetecting element of the same example.

  The impurity concentration profile of the P-type impurity in the base region 11 in the horizontal direction is inclined so as to decrease from the center of the base region 11 toward the gate electrode 5 side. That is, the P-type impurity concentration at the end of the base region 11 is lower than the P-type impurity concentration at the center of the base region 11. Thereby, in the vicinity of the gate electrode 5, the P-type impurity concentration of the base region 11 is low. In the photodetecting element 29, application of a voltage to the gate electrode 5 tends to deplete the base region 11 having a low impurity concentration in the vicinity of the gate electrode 5 and increase the current amplification factor. The impurity concentration profile in the depth direction of the photodetecting element 29 is the same as that in FIG.

  For example, the photodetection element 29 is an ion implantation process for forming the emitter region 9 (see FIG. 1) with respect to the manufacturing method example for producing the photodetection element 1 described with reference to FIGS. 6 (6).) Can be produced by changing the mask film 21.

  As mentioned above, although the Example of this invention was described, the numerical value, material, arrangement | positioning, number, etc. in the said Example are examples, This invention is not limited to these, It was described in the claim Various modifications are possible within the scope of the present invention.

  For example, in the above embodiment, the light detection element is an NPN bipolar transistor, but the light detection element of the present invention may be a PNP bipolar transistor. The PNP bipolar transistor can be realized, for example, by making the NPN bipolar transistor of the embodiment have the opposite conductivity type.

  Moreover, in the said Example, although the gate electrode 5 is a frame shape or a grid | lattice shape by planar view, the photon detection element of this invention is not limited to this. The light detection element of the present invention may have a configuration in which the electrodes are not in a frame shape or a lattice shape in plan view.

  Moreover, in the said Example, although the photon detection element is arranged in matrix form, this invention is not limited to this. In the light detection element of the present invention, the arrangement of the plurality of light detection elements is arbitrary. In addition, another element such as a read switch transistor may be arranged in a region where a plurality of light detection elements are arranged.

1, 23, 29 Photodetector 3b Epitaxial layer (semiconductor layer)
5 Gate electrode (electrode)
7 Gate insulating film (insulating film)
9, 25 Emitter region (first semiconductor region)
11 Base region (second semiconductor region)
13 Collector region (third semiconductor region)

JP2013-187527A

Claims (6)

An electrode, an insulating film, and a semiconductor layer including a first semiconductor region, a second semiconductor region, and a third semiconductor region,
The electrode is arranged embedded in the semiconductor layer along a first direction from the surface of the semiconductor layer to the inside,
The insulating film is disposed between the electrode and the semiconductor layer;
The first semiconductor region is of a first conductivity type and is disposed on a surface of the semiconductor layer;
The second semiconductor region is of a second conductivity type, and is disposed adjacent to the insulating film and the first semiconductor region;
The third semiconductor region is of a first conductivity type and is disposed adjacent to the second semiconductor region;
The impurity concentration of the second conductivity type impurity in the second semiconductor region is different from the first region of the second semiconductor region separated from the insulating film in a second direction orthogonal to the first direction, For the second region of the second semiconductor region closer to the insulating film than the first region, the impurity concentration of the second region is lower than the impurity concentration of the first region. A light detection element characterized by the above.   The photodetecting element according to claim 1, wherein the first semiconductor region is disposed away from the insulating film.   In the second semiconductor region, the second region is adjacent to the insulating film, the first region is adjacent to the first semiconductor region, and the impurity concentration of the second conductivity type impurity is the first concentration. The photodetecting element according to claim 2, wherein the photodetecting element is lowered from the region toward the second region.   4. The photodetecting element according to claim 2, wherein a position of a bottom portion of the first semiconductor region in the first direction is deeper than a position that is half the depth of the second semiconductor region in the first direction. .   5. The photodetecting element according to claim 2, wherein the first semiconductor region is formed of a semiconductor material embedded in the semiconductor layer from a surface of the semiconductor layer to an inside thereof.   6. The impurity concentration of the second conductivity type impurity in the second semiconductor region decreases from the first semiconductor region side toward the third semiconductor region side in the first direction. The light detection element according to any one of the above.

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